SIPPING D. Petrie
Internet-Draft SIPez LLC.
Intended status: Standards Track S. Channabasappa, Ed.
Expires: November 2, 2007 CableLabs
May 2007
A Framework for Session Initiation Protocol User Agent Profile Delivery
draft-ietf-sipping-config-framework-12
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Copyright (C) The IETF Trust (2007).
Abstract
This document specifies a framework to enable configuration of
Session Initiation Protocol (SIP) User Agents in SIP deployments.
The framework provides a means to deliver profile data that User
Agents need to be functional, automatically and with minimal
(preferably none) User and Administrative intervention. The
framework describes how SIP User Agents can discover sources, request
profiles and receive notifications related to profile modifications.
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As part of this framework, a new SIP event package is defined for
notification of profile changes. The framework provides minimal data
retrieval options to ensure interoperability. The framework does not
include specification of the profile data within its scope.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Executive Summary . . . . . . . . . . . . . . . . . . . . . . 6
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Reference Model . . . . . . . . . . . . . . . . . . . . . 7
4.2. Data Model and Profile Types . . . . . . . . . . . . . . 10
4.3. Profile Delivery Stages . . . . . . . . . . . . . . . . . 10
5. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.1. Simple Deployment Scenario . . . . . . . . . . . . . . . 11
5.2. Devices supporting multiple users from different
Service Providers . . . . . . . . . . . . . . . . . . . . 12
6. Profile Delivery Framework . . . . . . . . . . . . . . . . . . 15
6.1. Profile Delivery Stages . . . . . . . . . . . . . . . . . 15
6.1.1. Profile Enrollment . . . . . . . . . . . . . . . . . . 16
6.1.2. Content Retrieval . . . . . . . . . . . . . . . . . . 18
6.1.3. Change Notification . . . . . . . . . . . . . . . . . 18
6.1.4. Enrollment Data and Caching . . . . . . . . . . . . . 19
6.1.5. User Profile Type . . . . . . . . . . . . . . . . . . 22
6.2. Securing Profile Delivery . . . . . . . . . . . . . . . . 22
6.2.1. General Requirements . . . . . . . . . . . . . . . . . 23
6.2.2. Implementation Requirements . . . . . . . . . . . . . 23
6.2.3. Identities and Credentials . . . . . . . . . . . . . . 24
6.2.4. Securing Profile Enrollment . . . . . . . . . . . . . 25
6.2.5. Securing Content Retrieval . . . . . . . . . . . . . . 28
6.2.6. Securing Change Notification . . . . . . . . . . . . . 29
6.3. Additional Considerations . . . . . . . . . . . . . . . . 29
6.3.1. Profile Enrollment Request Attempt . . . . . . . . . . 29
6.3.2. Device Types . . . . . . . . . . . . . . . . . . . . . 33
6.3.3. Profile Data . . . . . . . . . . . . . . . . . . . . . 33
6.3.4. Profile Data Frameworks . . . . . . . . . . . . . . . 34
6.3.5. Additional Profile Types . . . . . . . . . . . . . . . 34
6.3.6. Deployment considerations . . . . . . . . . . . . . . 35
7. Event Package Definition . . . . . . . . . . . . . . . . . . . 35
7.1. Event Package Name . . . . . . . . . . . . . . . . . . . 36
7.2. Event Package Parameters . . . . . . . . . . . . . . . . 36
7.3. SUBSCRIBE Bodies . . . . . . . . . . . . . . . . . . . . 39
7.4. Subscription Duration . . . . . . . . . . . . . . . . . . 39
7.5. NOTIFY Bodies . . . . . . . . . . . . . . . . . . . . . . 40
7.6. Notifier Processing of SUBSCRIBE Requests . . . . . . . . 40
7.7. Notifier Generation of NOTIFY Requests . . . . . . . . . 41
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7.8. Subscriber Processing of NOTIFY Requests . . . . . . . . 41
7.9. Handling of Forked Requests . . . . . . . . . . . . . . . 42
7.10. Rate of Notifications . . . . . . . . . . . . . . . . . . 42
7.11. State Agents . . . . . . . . . . . . . . . . . . . . . . 42
8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
8.1. Example 1: Device requesting profile . . . . . . . . . . 42
8.2. Example 2: Device obtaining change notification . . . . . 45
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 49
9.1. SIP Event Package . . . . . . . . . . . . . . . . . . . . 49
9.2. Registry of SIP configuration profile types . . . . . . . 49
10. Security Considerations . . . . . . . . . . . . . . . . . . . 50
10.1. Local-network profile . . . . . . . . . . . . . . . . . . 52
10.2. Device profile . . . . . . . . . . . . . . . . . . . . . 53
10.3. User profile . . . . . . . . . . . . . . . . . . . . . . 54
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 55
12. Change History . . . . . . . . . . . . . . . . . . . . . . . . 55
12.1. Changes from
draft-ietf-sipping-config-framework-11.txt . . . . . . . 56
12.2. Changes from
draft-ietf-sipping-config-framework-10.txt . . . . . . . 56
12.3. Changes from
draft-ietf-sipping-config-framework-09.txt . . . . . . . 56
12.4. Changes from
draft-ietf-sipping-config-framework-08.txt . . . . . . . 57
12.5. Changes from
draft-ietf-sipping-config-framework-07.txt . . . . . . . 57
12.6. Changes from
draft-ietf-sipping-config-framework-06.txt . . . . . . . 58
12.7. Changes from
draft-ietf-sipping-config-framework-05.txt . . . . . . . 58
12.8. Changes from
draft-ietf-sipping-config-framework-04.txt . . . . . . . 59
12.9. Changes from
draft-ietf-sipping-config-framework-03.txt . . . . . . . 59
12.10. Changes from
draft-ietf-sipping-config-framework-02.txt . . . . . . . 59
12.11. Changes from
draft-ietf-sipping-config-framework-01.txt . . . . . . . 59
12.12. Changes from
draft-ietf-sipping-config-framework-00.txt . . . . . . . 60
12.13. Changes from
draft-petrie-sipping-config-framework-00.txt . . . . . . 60
12.14. Changes from draft-petrie-sip-config-framework-01.txt . . 60
12.15. Changes from draft-petrie-sip-config-framework-00.txt . . 61
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 61
13.1. Normative References . . . . . . . . . . . . . . . . . . 61
13.2. Informative References . . . . . . . . . . . . . . . . . 62
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 63
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Intellectual Property and Copyright Statements . . . . . . . . . . 64
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1. Introduction
SIP User Agents require configuration data to function properly.
Examples include local network, device and user specific information.
Ideally, this configuration process should be automatic and require
minimal or no user intervention.
Many deployments of SIP User Agents require dynamic configuration and
cannot rely on pre-configuration. This framework provides a standard
means of providing dynamic configuration which simplifies deployments
containing SIP User Agents from multiple vendors. This framework
also addresses change notifications when profiles change. However,
the framework does not define the content or format of the actual
profile data, leaving that to future standardization activities.
This document is organized as follows. Section 3 provides a brief
executive summary of the framework operation. Section 4 provides a
high-level overview of the abstract components, profiles, and profile
delivery stages. Section 5 provides some motivating use cases.
Section 6 provides details of the framework operation and
requirements. Section 7 provides a concise event package definition.
Section 8 follows with illustrative examples of the framework in use.
2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
This document also reuses the SIP terminology defined in [RFC3261]
and [RFC3265], and specifies the usage of the following terms.
Device: software or hardware entity containing one or more SIP user
agents. It may also contain entities such as a DHCP client.
Device Provider: the entity responsible for managing a given device.
Local Network Provider: the entity that controls the local network
to which a given device is connected.
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SIP Service Provider: the entity providing SIP services to users.
This can refer to private enterprises or public entities.
Profile: configuration data set specific to an entity (e.g., user,
device, local network or other).
Profile Type: a particular category of Profile data (e.g., User,
Device, Local Network or other).
Profile Delivery Server (PDS): the source of a Profile, it is the
logical collection of the Profile Notification Component (PNC) and
the Profile Content Component(PCC).
Profile Notification Component (PNC): the logical component of a
Profile Delivery Server that is responsible for enrolling devices
and providing profile notifications.
Profile Content Component (PCC): the logical component of a Profile
Delivery Server that is responsible for storing, providing access
to, and accepting profile content.
3. Executive Summary
The SIP UA Profile Delivery Framework uses a combination of SIP event
messages (SUBSCRIBE and NOTIFY; [RFC3265]) and traditional file
retrieval protocols, such as HTTP [RFC2616], to discover, monitor,
and retrieve configuration profiles. The framework defines three
types of profiles (local-network, device, and user) in order to
separate aspects of the configuration which may be independently
managed by different administrative domains. The initial SUBSCRIBE
for each profile allows the UA to describe itself (both its
implementation and its identity), while requesting access to a
profile by type, without prior knowledge of the profile name or
location. Discovery mechanisms are specified to help the UA form the
SUBSCRIBE request URI. The SIP UAS handling these subscriptions is
the Profile Delivery Server (PDS). When the PDS accepts a
subscription, it sends a NOTIFY to the device. The initial NOTIFY
from the PDS for each profile may contain profile data or a reference
to the location of the profile, to be retrieved using HTTP or similar
file transfer mechanisms. By maintaining a subscription to each
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profile, the UA will receive additional NOTIFY messages if the
profile is later changed. These may contain a new profile, a
reference to a new profile, or a description of profile changes,
depending on the Content-Type [RFC3261] in use by the subscription.
The framework describes the mechanisms for obtaining three different
profile types, but does not describe the data model they utilize (the
data model is out of scope for this specification).
4. Overview
This section provides an overview of the configuration framework. It
introduces the reference model and explains the Profile Delivery
Stages and the Profile Types. It is meant to serve as a reference
section for the document, rather than providing a specific logical
flow of material, as it may be necessary to revisit these sections
for a complete understanding of this document. The detailed
framework for the profile delivery, presented in Section 6, is based
on the concepts introduced in this section.
4.1. Reference Model
The design of the framework was the result of a careful analysis to
identify the configuration needs of a wide range of SIP deployments.
As such, the reference model provides for a great deal of
flexibility, while breaking down the interactions to their basic
forms which can be reused in many different scenarios.
The reference model for the framework defines the interactions
between the Profile Delivery Server(PDS) and the device. The device
needs the profile data to effectively function in the network. The
PDS is responsible for responding to device requests and providing
the profile data. The reference model is illustrated in Figure 1.
+-------------------------+
+--------+ | Profile Delivery Server |
| Device |<==========================>| +---+ +---+ |
+--------+ | |PNC| |PCC| |
| +---+ +---+ |
+-------------------------+
PNC = Profile Notification Component
PCC = Profile Content Component
Figure 1: Framework Reference Model
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The PDS is subdivided into two logical components:
o Profile Notification Component (PNC), responsible for enrolling
devices for profiles and providing profile change notifications;
o Profile Content Component (PCC), responsible for storing,
providing access to, and accepting modifications related to
profile content.
The preceding framework reference model can be applied in a variety
of deployments scenarios. Two deployment scenarios representing
different ends of the complexity spectrum are presented.
In the simplest scenario, a device connects through a network that is
controlled by a single provider who provides the local-network,
manages the devices, and offers services to the users. The provider
propagates profile data to the device that contains all the necessary
information to obtain services in the network (including information
related to the local-network and the users). This is illustrated in
Figure 2.
--------------
/ Local-network, \
| Device & Service |
\ Provider /
----------------
|
|
--------
| Device |
--------
|
|
----
|User|
----
Figure 2: Simple System Level Model
In more complex deployments, devices connect via a local network that
is not controlled by the SIP Service Provider, such as devices that
connect via available public WiFi hotspots. In such cases, local
network providers may wish to provide local network information such
as bandwidth constraints to the devices.
Devices may also be controlled by device providers that are
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independent of the SIP service provider who provides user services,
such as kiosks that allow users to access services anywhere. In such
cases the profile data may have to be obtained from different profile
sources: local network provider, device provider and SIP service
provider. This is indicated in Figure 3 .
--------
/ SIP \
| Service | -> Provides 'user' profile
| Provider | data (e.g., services
\ / configuration)
-------- --------
| / \
| | Device | -> Provides 'device' profile
| | Provider | data (e.g., device specifics)
| \ /
| ---------
| /
| / -------
| / / Local \
| / | Network |
| | | Provider | -> Provides 'local-network' profile
| | \ / data (e.g., bandwidth)
| | -------
| | /
| | /
| | |
===================
( Local Network )
===================
|
|
--------
| Device | -> Needs the 'local-network'
-------- and 'device' profile
/ \
/ \
------ ------
|User A| |User B| -> Users need 'user' profiles
------ ------
Figure 3: General System Level Model
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As illustrated, the simplest deployments present a single profile
source whereas others may present multiple profile sources. To
address a vast majority of deployments, this framework specifies
three distinct profiles, each of which can be obtained from a
different provider, and set of a profile delivery stages that are
common to any profile type.
The understanding is that deployments in general will support the
defined profile types. However, the framework allows for flexibility
in specialized cases. PDSs and devices will implement all the three
profile types. Unless configured otherwise, a device will try to
obtain all the three profile types. A retrieval order is specified
for the profile. Additional profiles may also be specified outside
the scope of this document, but are expected to follow the same
profile delivery stages.
4.2. Data Model and Profile Types
This framework specifies the following three profiles. Additional
extended profiles may also be defined.
Local Network Profile: contains configuration data related to the
local network to which a device is directly connected. It is
expected to be provided by the Local Network Provider.
Device Profile: Contains configuration data related to a specific
device, provided by the Device Provider.
User Profile: contains configuration data related to a specific
User, as required to reflect that user's preferences and the
particular services subscribed to. It is expected to be provided
by the SIP Service Provider.
4.3. Profile Delivery Stages
The framework specified in this document requires a device to
explicitly request profiles. It also requires one or more PDSs which
provide the profile data. The processes that lead a device to obtain
profile data, and any subsequent changes, can be explained in three
stages, termed the Profile Delivery Stages.
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Profile Enrollment: the process by which a device requests, and if
successful, enrolls with a PDS capable of providing a profile. A
successful enrollment is indicated by a notification containing
the profile information (contents or content indirection
information). Depending on the request, this could also result in
a subscription to notification of profile changes.
Profile Content Retrieval: the process by which a device retrieves
profile contents, if the profile enrollment resulted in content
indirection information.
Profile Change Notification: the process by which a device is
notified of any changes to an enrolled profile. This may provide
the device with modified profile data or content indirection
information.
5. Use Cases
This section provides a small, non-comprehensive set of
representative use cases to further illustrate how this Framework can
be utilized in SIP deployments. The first use case is simplistic in
nature, where as the second is relatively complex. The use cases
illustrate the effectiveness of the framework in either scenario.
For Security Considerations please refer to Section 6 and Section 10.
5.1. Simple Deployment Scenario
Description: Consider a deployment scenario (e.g., a small private
enterprise) where a single entity enables the local network, manages
deployed devices and provides SIP services. The devices only attach
to the local network, and are pre-configured with a single user.
The following assumptions apply:
o The device profile data contains all the information necessary
for the device to participate in the local network and obtain
services.
o The device is pre-configured to only request the device profile.
o The enrollment notification contains the profile data (profile
content retrieval is not required).
o There are no proxies in the network.
Figure 4 illustrates this use case and highlights the communications
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relevant to the framework specified in this document.
+----------------------+
+--------+ | Local Network, Device|
| Device | |& SIP Service Provider|
| | | |
+--------+ | DHCP PDS |
+----------------------+
| | |
(A) |<============== DHCP =============>| |
| |
| |
| |
(B) |<=========== Profile Enrollment ============>|
| | Profile data
| | is modified
| |
(C) |<============ Profile Change ================|
| Notification |
| |
| |
Figure 4: Use Case 1
The following is an explanation of the interactions in Figure 4.
(A) Upon initialization, the device obtains IP configuration
parameters using DHCP.
(B) The device performs Profile Enrollment for the device profile;
the device profile data is contained in the enrollment
notification.
(C) Due to a modification of the device profile, a Profile Change
Notification is sent across to the device, along with the
modified profile.
5.2. Devices supporting multiple users from different Service Providers
Description: Consider a single device (e.g., Kiosk at an airport)
that allows for multiple users to obtain services from a list of pre-
configured SIP Service Providers.
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The following assumptions apply:
o Provider A is the Device and Local Network Provider for the
device, and the SIP Service Provider for user A; Provider B is
the SIP Service Provider for user B.
o Profile enrollment always results in content indirection
information requiring profile content retrieval.
o Communication between the device and the PDSs is facilitated by
SIP proxies.
Figure 4 illustrates the use case and highlights the communications
relevant to the framework specified in this document.
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User User
A B +----------------------+ +----------------------+
+--------+ | Provider | | Provider |
| Device | | A | | B |
| | | | | |
+--------+ | DHCP PROXY PDS | | PROXY PDS |
+----------------------+ +----------------------+
| | | | | |
(A) |<====DHCP====>| | | | |
| | | | |
| | | | |
| Profile Enrollment | | | |
(B) |<local-network profile>|<====>| | |
|
| <<Profile content retrieval>>
|
|
| Profile Enrollment | | | |
(C) |<== device profile ==> |<====>| | |
|
| <<Profile content retrieval>>
|
.
.
.
[[User A obtains services]]
| Profile Enrollment | | | |
(D) |<= user profile (A) => |<====>| | |
| | | | |
|
| <<Profile content retrieval>>
.
.
.
.
[[User B obtains services]]
|
| Profile Enrollment | |
(E) |<=========== user profile (B) ==========>|<=========>|
| | |
| <<Profile content retrieval>>
|
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Figure 5: Use Case 2
The following is an explanation of the interactions in Figure 5.
(A) Upon initialization, the device obtains IP configuration
parameters using DHCP. This also provides the local domain
information to help with local-network profile enrollment.
(B) The device requests profile enrollment for the local network
profile. It receives an enrollment notification containing
content indirection information from Provider A's PDS. The
device retrieves the profile (this contains useful information
such as firewall port restrictions and available bandwidth).
(C) The device then requests profile enrollment for the device
profile. It receives an enrollment notification resulting in
device profile content retrieval. The device initializes the
User interface for services.
(D) User A with a pre-existing service relationship with Provider A
attempts communication via the user Interface. The device uses
the user supplied information (including any credential
information) and requests profile enrollment for user A's
profile. Successful enrollment and profile content retrieval
results in services for user A.
(E) At a different point in time, user B with a service relationship
with Provider B attempts communication via the user Interface.
It enrolls and retreives user B's profile and this results in
services for user B.
6. Profile Delivery Framework
This section presents the profile delivery framework, the subject of
this document. The section starts by explaining the framework via
the profile delivery stages. It then explains how the framework
secures the profile data propagation. It ends with considerations
such as back-off and retry mechanisms and profile data.
6.1. Profile Delivery Stages
There are three profile delivery stages: profile enrollment, content
retrieval and change notification.
The first step is profile enrollment and serves two purposes. It
allows a device to enroll with a PDS. It also allows the PDS to
receive the request, authenticate if necessary, authorize and enroll
the device.
If the device enrolls successfully, the PDS transmits a notification
to the device. This notification contains either the requested
profile data, or content indirection information indicating the PCC
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that can provide the profile data. Usage of content indirection is
optional. When employed, the retrieval of the profile data is
described by the stage termed content retrieval.
Based on the enrollment request, the PDS may enroll the device for a
period in time during which the device is notified of any profile
changes. This stage is termed change notification.
The stages apply to any profile specified by this framework. Devices
and PDSs MUST comply with the requirements as specified in this
section. The details and the requirements are specified below.
6.1.1. Profile Enrollment
Profile enrollment is the process by means of which a device
requests, and receives, profile data. Each profile type specified in
this document requires an independent enrollment request. However, a
particular PDS can support enrollment for one or more profile types.
Profile enrollment consists of the following operations, in the
specified order.
Enrollment request transmission
Profile enrollment is initiated when the device transmits an
enrollment request using a SIP SUBSCRIBE request [RFC3265] for the
event package specified in Section 7.2. The profile being
requested is indicated using the 'profile-type' parameter. The
device MUST transmit the SIP SUBSCRIBE message in accordance with
RFC 3263 [RFC3263].
The device needs certain data to create an enrollment request.
This includes the profile provider's domain name, identities and
credentials. Such data can be "configured" during device
manufacturing, by the user prior to network connectivity, or via
profile data retrieval. It can also be "discovered" using the
procedures specified by this framework. The "discovered" data can
be retained across device resets (but not across factory resets)
and such data is refered to as "cached". Thus, data can be
cached, configured or discovered. The following rules apply.
* If the device is configured with a specific domain name (for
the local network provider or device provider), it MUST NOT
attempt re-discovery of the domain name.
* The device MUST only use data associated with the provider's
domain in an enrollment request. As an example, when the
device is requesting a local-network profile in the domain
'example.net', it cannot present a user AoR associated with the
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local domain 'example.com'.
* The device SHOULD adhere to the following order of data usage:
cached, configured, and discovered. An exception is when the
device is explicitly configured to use a different order.
Upon failure to obtain the profile using any methods specified in
this framework, the device MAY provide a user interface to allow
for user intervention. This can result in temporary, one-time
data to bootstrap the device. Such temporary data is not
considered to be "configured" and is not expected to be cached
across resets. The configuration obtained using such data MAY
provide the configuration data required for the device to continue
functioning normally.
Devices attempting enrollment MUST comply with the SIP-specific
event notification specified in [RFC3265], the event package
requirements specified in Section 7.2, and the security
requirements specified in Section 6.2.
Enrollment request admittance
A PDS or a SIP infrastructure element (such as a SIP proxy) will
receive a transmitted enrollment request. If a SIP infrastructure
element receives the request, it will relay it to the
authoritative proxy for the domain indicated in the Request-URI.
The authoritative proxy is required to examine the request (e.g.,
event package) and transmit it to a PDS capable of addressing the
profile enrollment request.
A PDS receiving the enrollment request SHOULD respond to the
request, or proxy it to a PDS that can respond. An exception is
when the a policy prevents a response (e.g., recognition of a DoS
attack, an invalid device, etc.). The PDS then verifies the
identity presented in the request and performs any necessary
authentication. Once authentication is successful, the PDS MAY
admit or reject the enrollment request, based on applicable
authorization policies. A PDS admitting the enrollment request
indicates it via a 2xx-class response, as specified in [RFC3265].
Refer to Section 7.6 and Section 6.2 for more information on
subscription request handling and security requirements,
respectively.
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Enrollment request acceptance
A PDS that admits the enrollment request verifies applicable
policies, identifies the requested profile data and prepares a SIP
notification to the device. Such a notification can either
contain the profile data or contain content indirection
information that results in the device performing profile content
retrieval. The PDS then transmits the prepared SIP notification.
When the device successfully receives and accepts the SIP
notification, profile enrollment is complete.
When it receives the SIP notification indicating enrollment
acceptance, the device MUST make the new profile effective within
the specified timeframe, as described in Section 7.2.
Once profile enrollment is successful, the PDS MUST consider the
device enrolled for the specific profile, for the duration of the
subscription.
6.1.2. Content Retrieval
A successful profile enrollment leads to an initial SIP notification,
and may result in subsequent change notifications. Each of these
notifications can either contain profile data, or content indirection
information. If it contains content indirection information, the
device is required to retrieve the profile data using the specified
content retrieval protocols. This process is termed profile content
retrieval. For information regarding the content of the notification
body please refer to Section 7.5.
Devices and PDSs implementing this framework MUST implement two
content retrieval protocols: HTTP and HTTPS as specified in [RFC2616]
and [RFC2818], respectively. Future enhancements or usage of this
framework may specify additional or alternative content retrieval
protocols. For security requirements and considerations please refer
to Section 6.2.
6.1.3. Change Notification
Profile data can change over time. Changes can be initiated by
various entities (e.g., via the device, back-office components and
end-user web interfaces) and for various reasons (e.g., change in
user preferences and modifications to services). When a profile is
changed the PDS MUST inform all the devices currently enrolled for
the specific profile. This process of informing a device of any
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changes to the profile that it is currently enrolled for is termed
change notification.
The PDS provides change notification using a SIP notification (SIP
NOTIFY message as specified in [RFC3265]). The SIP notification may
provide the changes, a revised profile or content indirection which
contains a pointer to the revised data. When a device successfully
receives a profile change notification for an enrolled profile, it
MUST act upon the changes prior to the expiration of the 'Expires'
parameter.
For NOTIFY content please refer to Section 7.5.
6.1.4. Enrollment Data and Caching
To enroll, the device needs to request enrollment. This is done via
a SIP SUBSCRIBE message. The requirements for the contents of the
SIP SUBSCRIBE are described in this section. The data required can
be configured, cached or discovered - depending on the profile type.
If the data is not configured, the device MUST use relevant cached
data or proceed with data discovery. This section describes the
requirements for creating a SIP SUBSCRIBE for enrollment, the caching
requirements and how data can be discovered.
6.1.4.1. Local-Network Profile
To request the local-network profile a device needs the local network
domain name, a device identifier and optionally a user AoR with
associated credentials (if one is configured). Since the device can
be potentially initialized in a different local-network each time, it
SHOULD NOT cache the local network domain or SIP subscription URIs
across resets. An exception to this is when the device can confirm
that it is reinitialized in the same network (using means outside the
scope of this document). Thus, in most cases, the device needs to
discover the local network domain name. The device discovers this by
establishing IP connectivity in the local network. Once established,
the device MUST use the local network domain obtained using static
configuration. If it is not configured, it MUST employ dynamic
discovery using DHCPv4 ([RFC2132], Domain Name option) or DHCPv6
([RFC4704]). Once the local network domain is obtained, the device
creates the SIP SUBSCRIBE for enrollment as described below.
o The device MUST NOT populate the user part of the Request URI.
The device MUST set the host and port of the Request URI to the
concatenation of "_sipuaconfig" and the local network domain/port.
o If the device has been configured with a user AoR for the local
network domain (verified as explained in Section 6.2) it MUST use
it to populate the "From" field, unless explicity configured not
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to (due to privacy concerns, for example). If not, the device
MUST set the "From" field to a value of
"anonymous@anonymous.invalid".
o The device MUST include the +sip.instance parameter within the
'Contact' header, as specified in [I-D.ietf-sip-outbound]. The
device MUST ensure that the value of this parameter is the same as
that included in the device profile enrollment request.
For example, if the device requested and received the local domain
name via DHCP to be: airport.example.net, then the local-network
Profile SUBSCRIBE Request URI would look like:
sip:_sipuaconfig.airport.example.net
The local-network profile SUBSCRIBE Request URI does not have a user
part so that the URI is distinct between the "local" and "device"
URIs when the domain is the same for the two. This provides a means
of routing to the appropriate PDS in domains where there are distinct
servers.
The From field is populated with the user AoR, if available. This
allows the local network provider to propagate user-specific profile
data, if available. The "+sip.instance" parameter is set to the
device identifier or specifically, the SIP UA instance. Even though
every device may get the same (or similar) local-network Profile, the
uniqueness of the "+sip.instance" parameter provides an important
capability. Having unique From fields allows the management of the
local network to track devices present in the network and
consequently also manage resources such as bandwidth allocation.
6.1.4.2. Device Profile Type
The device profile is intended for obtaining information from the
device provider managing the device. To request the device profile,
the device needs a unique device identifier, the device provider's
domain name and optionally a device AoR (if configured). The device
AoR is an AoR associated with the device for obtaining device
profiles. This is considered to be a special 'user AoR' for the
device profile, and can be the same as a user AoR associated with the
device.
Once a provider is associated with a device, the device provider will
not change frequently (an example of a change is the re-use of the
same device while changing device providers). Thus, the device
SHOULD cache the Subscription URI for the device profile upon
successful enrollment, and use it upon reset. Exceptions include
cases where the device identifier has changed (e.g., new network card
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with a new MAC address), device provider information has changed
(e.g., user initiated change) or the device cannot obtain its profile
using the Subscription URI.
If it is not configured, then the device MUST use a cached, or
discovered domain name. If the device does not have a configured or
cached Subscription URI, then it can use the device AoR. If that is
unavailable, it can use the configured device provider's domain to
form the subscription URI.
The following options are provided for device provider's domain
discovery (used only when it is not configured with one). The device
MUST use the results of each successful discovery process for one
enrollment attempt, in the order specified below.
o Option 1: Devices that support DHCP MUST attempt to obtain the
host and port of the outbound proxy during the DHCP process, using
the DHCP option for SIP servers defined in [RFC3361] or [RFC3319]
(for IPv4 and IPv6 respectively). The values are then used to
populate the Request URI.
o Option 2: Devices that support DHCP MUST attempt to obtain the
local IP network domain during the DHCP process (refer to
[RFC2132] and [RFC4704] ) and use this as the host portion of the
Request URI.
o Option 3: Devices MUST use the local network domain name
(configured or discovered to retrieve the local-network profile),
prefixing it with the label "_sipuaconfig". This is then used as
the host portion of the Request URI.
If the device has to create a new Subscription URI (i.e., from a
configured domain name, or if the cached URI is unusable) the
following requirements apply.
o The device MUST set the Request URI to the device AoR, if known.
If it is unavailable or the enrollment fails, the device MUST use
the device identifier (specified later in this section) along with
the device provider's domain name and port (configured or
discoverd) to form the Request URI.
o If the device has been configured with a device AoR, then it MUST
use it to populate the "From" field. If not, the device MUST set
the "From" field to a value of anonymous@<device provider's
domain>.
o The device MUST include the +sip.instance parameter within the
'Contact' header, as specified in [I-D.ietf-sip-outbound]. The
device MUST use the same value as the one presented while
requesting the local-network profile.
When the device needs to present its device identifier it MUST use
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the UUID-based URN representation for the user portion of the
Request-URI, as specified in [RFC4122]. The following requirements
apply:
o When the device has a non-alterable MAC address it SHOULD use
version 1 UUID representation with the timestamp and clock
sequence bits set to a value of '0'. This will allow for easy
recognition, and uniqueness of MAC address based UUIDs. An
exception is the case where the device supports independent device
configuration for more than one SIP UA. An example would be
multiple SIP UAs on the same platform.
o If the device cannot use a non-alterable MAC Address, it MUST use
the same approach as defining a user agent Instance ID in
[I-D.ietf-sip-outbound].
o When the URN is used as the user part of the Request URI, it MUST
be URL escaped
The colon (":") is not a legal character (without being
escaped) in the user part of an addr-spec ([RFC4122]).
For example, the instance ID:
urn:uuid:f81d4fae-7ced-11d0-a765-00a0c91e6bf6@example.com
would be escaped to look as follows in a URI:
sip:urn%3auuid%3af81d4fae-7ced-11d0-a765-00a0c91e6bf6@
example.com
The ABNF for the UUID representation is provided in [RFC4122]
6.1.5. User Profile Type
The user profile allows a SIP Service Provider to provide user-
specific configuration. This is based on a user AoR that is known by
the PDS and statically or dynamically configured on the device (e.g.,
user entered or propagated as part of the device or other profile).
Similar to device profiles, the content and propagation of user
profiles may differ, based on deployment scenarios (e.g., users
belonging to the same domain may - or may not - be provided the same
profile). This framework does not specify any discovery mechanisms
for this profile type. Unless configured, the device cannot, and
MUST NOT, request the user profile.
6.2. Securing Profile Delivery
This section further explains the profile delivery stages.
Specifically, it presents the requirements necessary to secure
profile delivery.
It is to be noted that future enhancements to the framework may
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specify additional or alternative behavior. Any such enhancements
should be cryptographically equivalent to, or increase, the
requirements presented in this document.
For security threats and considerations addressed by this section
please refer to Section 10.
6.2.1. General Requirements
Profile data retrieval starts with profile enrollment. The device
forms a SIP subscription as specified in Section 6.1.4 and transmits
it to the SIP entity resulting from the procedures specified in
[RFC3263]. The entity to which it transmits the profile enrollment
is termed the 'next-hop SIP entity'. It can be a SIP proxy or a PDS.
This framework utilizes TLS ([RFC4346]) and 'Server Identity'
verification as specified in [RFC2818], Section 3.1. The 'Server
Identity' in this case is always the domain of the next-hop SIP
entity. The verifier is the device. A TLS session that results from
a successful verification of the next-hop SIP entity is termed a
'Server identity verified TLS session' or 'next-hop entity verified
TLS session'.
6.2.2. Implementation Requirements
The following are the general implementation requirements.
- A device MUST implement TLS ([RFC4346]) with support for Server
Identity verification as specified in [RFC2818]
- PDSs SHOULD contain X.509 certificates that can allow for PDS
authentication using the procedures specified in [RFC2818].
Exceptions are PDSs that do not propagate sensitive profile data
(e.g., a local-network PDS that does not support sensitive profile
data).
- PDSs that are configured with X.509 certificates (as described
above) MUST implement TLS [RFC4346] and support 'Server Identity'
verification as specified by [RFC2818].
- PDSs that are configured with X.509 certificates (as described
above) SHOULD implement SIP Identity as specified in [RFC4474]. When
the SIP Identify header is included, the PDS MUST set the host
portion of the AoR in the 'From' header to the local network domain.
It is to be noted that the requirement to implement TLS does not
imply its usage in all cases. Please refer to the rest of this
section for usage requirements.
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6.2.3. Identities and Credentials
To enroll for a profile, the device needs to provide an identity.
This can be a user AoR (local-network and user profiles), a device
AoR (device profile), the device identity (device profile), or a
framework-specified identity (local-network profile).
To be able to present an identity, such as a user AoR, the device
needs to be configured. This can be accomplished in one of many
ways:
Pre-configuration
A distributor of the device may pre-configure the device with
identities and associated credentials. Identities refers to a
device AoR (for use with the device profile) or a user AoR.
Out-of-band methods
A device or SIP service provider may provide the end-user with
hardware- or software-based devices that contain the identities
and associated credentials. Examples include SIM cards and USB
drives.
End-user interface
The end-user may be provided with user AoRs and credentials. The
end-user can then configure the device (using a user interface),
or present when required (e.g., IM login screen).
Using this framework
When a device is initialized, even if it has no pre-configured
information, it can request the local-network and device profiles.
In such a case the device profile can provide three kinds of
information:
* Profile data that allows the end-user to communicate with the
device or SIP service provider. The provider can then use any
applicable method (e.g., web portal) to provide the user AoR.
* Profile data that redirects the device to an entity, such as
the PCC, that can provide identity data. As an example,
consider a device that has a X.509 certificate that can be
authenticated by the PCC. In such a case, the PCC can use
HTTPS to provide the user AoR.
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* Profile data containing user identity to be used. This can be
used in cases where the device is initialized for the first
time, or after a factory reset, in the device provider's
network.
If a device presents a user AoR in the enrollment request, the PDS
can challenge it. To respond to such authentication challenges, the
device needs to have associated credentials. Thus, any of the
configuration methods indicated above need to provide the user
credentials along with any AoRs.
Additionally, AoRs are typically known by PDSs that serve the domain
indicated by the AoR. Thus, devices can only present the configured
AoRs in the respective domains. An exception is the use of federated
identities. This allows a device to use a user's AoR in multiple
domains.
The configured user or device AoR and associated credentials can be
used in applicable domains for any of the profile types specified by
this framework. In the absence of the device or user AoR, the device
is not expected to contain any other credentials. Future
enhancements can specify additional identities and credentials.
6.2.4. Securing Profile Enrollment
A device requests profile data by transmitting an enrollment request
using cached, configured or discovered data. The enrollment request
is received by a PDS that verifies the profile type and the identity
presented, such as a user AoR. If the device presents a configured
user identity, it is more likely to be known by the network and
associated with credentials. If not (e.g., discovered or device
identities) it may not be known by the PDS (and hence, may not be
associated with credentials).
If the user identity presented in the enrollment request is known by
the PDS, it MUST challenge the request; an exception is the case
where the data being provided is not particular to the presented user
identity. If the device successfully responds to the challenge, it
is provided the initial notification which contains the profile data
within, or via content indirection.
To ensure that the PDS providing the data belongs to the domain
associated with the identity, the device SHOULD authenticate the
source of the notifications. Since the device only directly
communicates with the next-hop SIP entity (which may or may not be
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the PDS) it SHOULD establish a 'next-hop SIP entity authenticated TLS
session prior to transmitting the enrollment request. The next-hop
SIP entity SHOULD have a secure communications channel with the PDS.
If not, the PDS SHOULD provide the notifications and include the SIP
Identity header. If the PDS wants to ensure privacy in such
situations, it MAY provide only content indirection information in
the notifications. Content indirection which results in a secure
communications channel, such as HTTPS, will ensure data integrity and
protection.
Profile-specific requirements follow.
6.2.4.1. Local-network profile
Device Requirements
- If the device has a configured user AoR associated with the
local network domain then the device SHOULD establish a Server
Identity verified TLS session with the next-hop SIP entity.
Exceptions are cases where the device is configured not to do so
(e.g., via previously obtained, authenticated profile data).
- If the device does not have a configured user AoR it MAY still
establish a next-hop entity verified TLS session.
- If an attempted next-hop SIP entity verified TLS session
succeeds:
* the device MUST transmit the enrollment request with the user
AoR (if configured);
* the device MUST respond to an authentication challenge.
- If the TLS session fails to verify the next-hop SIP entity
(i.e., the domain name could not be verified) the device MUST NOT
continue with the current enrollment request. However, the device
MUST retry by trying to establish server identity verified TLS
sessions with other next-hop entities (obtained via [RFC3263]. If
the list of next-hop entities has been exhausted then:
* if the device has a user interface, and unless explicity
configured not to, the device SHOULD prompt the user if it can
continue without TLS;
* unless indicated otherwise via configuration or the user, the
device MUST retry enrollment without TLS and without the user
AoR.
- If an attempted next-hop SIP entity verified TLS session fails
(i.e., the PDS does not support TLS) the device MUST transmit the
enrollment request, without the user AoR.
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- In the absence of a Server Identity authenticated TLS session
with the next-hop SIP entity:
* the device MUST NOT respond to any authentication challenges;
* the device MUST ignore notifications containing sensitive
profile data.
PDS Requirements
- If an enrollment request contains a user AoR that will result in
user-specific profile data, then the PDS MUST successfully
authenticate the user before providing user-specific profile data
- If user authentication fails the PDS MAY refuse enrollment,
or provide profile data without the user-specific information.
- It is to be noted that if a PDS attempts authentication
without an existing next-hop authenticated TLS session, it will
fail.
- A PDS that does not support TLS MUST use content indirection to
a PCC that supports authentication and integrity protection for
conveying sensitive profile data.
- If the enrollment request did not occur over a next-hop
authenticated TLS session, a PDS that supports SIP Identity MUST
include the SIP Identity header in the initial and subsequent
change notifications
6.2.4.2. Device profile
Device Requirements
A device presents either a device identity or a configured device
AoR to obtain the device profile. If configured with a device
AoR, it can either be a SIPS URI or a SIP URI. If it is not pre-
configured then the device uses the device identifier in
association with methods specified [RFC3263].
If the device is using the methods specified in [RFC3263] it MUST
prefer SIPS over SIP.
If it obtains a SIPS URI for the next-hop SIP entity, the device
MUST attempt to establish next-hop authenticated TLS session (as
specified in [RFC3261]).
If the device is configured with a device AoR and it successfully
establishes a next-hop authenticated TLS session then it MUST
respond to an authentication challenge.
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In any case, if the TLS establishment fails (e.g., the PDS does
not implement TLS) or it is unsuccessful (e.g., the connecting SIP
entity is not the expected domain) the device MUST consider this
an enrollment failure and try an alternate next-hop SIP entity (or
declare an enrollment failure if all the attempts have been
exhausted).
In the absence of a next-hop SIP entity authenticated TLS session:
- the device MUST NOT respond to any authentication challenges;
- the device MUST ignore notifications containing sensitive
profile data.
PDS Requirements
PDS requirements are the same as that of the local-network
profile, with one addition. A PDS MUST NOT accept enrollment
requests with a SIPS URI in the absence of a secure communications
channel (such as a TLS session from the device or a trusted
proxy).
6.2.4.3. User profile
A device requesting a user profile will use a user AoR that is either
a SIP URI or a SIPS URI. In either case, the requirements for the
device and the PDS are the same as when the device requests a device
profile.
In addition, PDSs MUST NOT accept user profile enrollment requests
for unknown users.
6.2.5. Securing Content Retrieval
Initial or change notifications following a successful enrollment can
either provide a device with the requested profile data, or use
content indirection and redirect it to a PCC that can provide the
profile data. This document specifies HTTP and HTTPS as content
retrieval protocols.
If the profile is provided via content indirection and contains
sensitive profile data then the PDS MUST use a HTTPS URI for content
indirection. PCCs and devices MUST NOT use HTTP for sensitive
profile data. A device MUST authenticate the PCC as specified in
[RFC2818], Section 3.1.
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6.2.6. Securing Change Notification
A successful profile enrollment results in an initial notification.
If the device requested enrollment via a SIP subscription with a non-
zero 'Expires' parameter, it can also result in change notifications
for the duration of the subscription.
If the device established next-hop authentication TLS then any such
notifications SHOULD be sent over the same TLS session. If the TLS
session exists, the device MUST ignore any notifications sent outside
the TLS session. If no such TLS session exists, the PDS MUST NOT
include any sensitive profile data. If no such TLS session exists,
the PDS MUST NOT accept any sensitive profile data and ignore such
notifications.
A PDS that does not support TLS MUST use content indirection to a PCC
that supports authentication and integrity protection for conveying
sensitive profile data.
6.3. Additional Considerations
This section provides additional considerations such as further
details on enrollment with related backoff and retry methods,
guidelines on profile data and additional profile types.
6.3.1. Profile Enrollment Request Attempt
A state diagram representing a device requesting any specific profile
defined by this framework is shown in Figure 6.
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+------------+
| Initialize |
+-----+------+
|
|
V
+-------------+
| Prepare |
+--------->| Enrollment |<------------------+
| | Request | |
| +------+------+ |
+------+------+ | |
| Failure | Enroll. Req. prepared |
+-->| Handling & | /Send Req |
| | Delay | | |
| +-------------+ V |
| ^ ^ +-------------+ |
| | | | Await | |
| | +--------+ Enrollment | |
| | Timeout, | acceptance | |
| | non-2xx/- +------+------+ |
| | | |
| Timeout 200 OK/- Enrollment
| /Terminate | Timeout/-
| Enrollment V |
| | +--------------+ |
| | | Enrollment | |
| +------------+ accepted | |
Retries Exceeded |(await NOTIFY)| |
/Retry Enrollment +---+------+---+ |
| | | |
| | | |
| NOTIFY w. Content Ind| | NOTIFY w. Profile |
| /Retrieve Profile | | /Accept Profile |
| +------------+ +------------+ |
| | | |
| V V |
| +------------+ +------------+ |
+-----+ Retrieving | Retrieved | Enrollment +---+
,->| Profile +--/Apply Profile-->| Successful |
/ | | |(monitoring)|<--.
Timeout +--+---------+ +--+----+----+ :
/Retry ; ^ | : ;
`------' | NOTIFY w. Cont.Ind | `-------'
+---/Retrieve Profile-----+ NOTIFY w. Profile
/Apply Profile
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Figure 6: Device State Diagram
As a reminder:
o The timeout for SIP messages is specified by [RFC3261]
o The timeout for profile retrieval using content indirection will
be as specified by profile retrieval protocols employed
In addition, since profile enrollment is a process unique to this
framework, the device MUST follow the enrollment attempt along with
exponential backoff and retry mechanisms as indicated in Figure 7.
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Function for Profile Enrollment ()
Iteration i=0
Loop: Attempt
Loop: For each SIP Subscription URI
Loop: For each next-hop SIP entity obtained via RFC3263
- Prepare & transmit Enrollment Request
- Await Enrollment Acceptance and initial NOTIFY
+ If the profile enrollment is successful
= Abort this function()
+ If profile enrollment fails due to an explicit
failure or a timeout as specified in RFC3261
= Continue with this function()
End Loop: Next-hop SIP entity contact
End Loop: SIP Subscription URI formation
(Note: If you are here, profile enrollment did not succeed)
+ Is any valid cached profile data available?
= If yes, use it and continue with this function()
+ If the enrollment request is for a non-mandatory profile
= then spawn the next profile and continue with this
function()
- Delay for 2^i*(64*T1); -- this is exponential backoff
- increment i;
- If i>8, reset i=0;
End loop: Attempt
End Function()
Figure 7: Profile Enrollment Attempt (pseudo-code)
The pseudo-code above (Figure 7) allows for cached profiles to be
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used. However, any cached Local Network profile MUST NOT be used
unless the device can ensure that it is in the same local network
which provided the cached data. This framework does not provide any
procedures for local network recognition. Any cached device and user
profiles MUST only be used in domains that they are associated with.
For example, a cached device profile is used only when the associated
domain matches the current device provider's domain. If a PDS wants
to invalidate a profile it may do so by transmitting a NOTIFY with an
'empty profile' (not to be confused with an empty NOTIFY). A device
receiving such a NOTIFY MUST discard the applicable profile (i.e., it
cannot even store it in the cache). Additionally, if a factory reset
is available and performed on a device, it MUST reset the device to
its initial state prior to any configuration. Specifically, the
device MUST set the device back to the state when it was originally
distributed.
The order of profile enrollment is important. For the profiles
specified in this framework, the device must enrol in the order:
local-network, device and user. The pseudo-code presented earlier
(Figure 7) differentiates between 'mandatory' and 'non-mandatory'
profiles. This distinction is left to profile data definitions.
It is to be noted that this framework does not allow the devices to
inform the PDSs of profile retrieval errors such as invalid data.
Follow-on standardization activities are expected to address this
feature.
6.3.2. Device Types
The examples in this framework tend to associate devices with
entities that are accessible to end-users. However, this is not
necessarily the only type of device that can utilize the specified
Framework. Devices can be entities such as SIP Phones or soft
clients, with or without user interfaces (that allow for device
Configuration), entities in the network that do not directly
communicate with any users (e.g., gateways, media servers, etc) or
network infrastructure elements e.g., SIP servers).
6.3.3. Profile Data
This framework does not specify the contents for any profile type.
Follow-on standardization activities are expected to address profile
contents. However, the framework provides the following requirements
and recommendations for profile data definitions:
o The device profile type MUST specify parameters to configure the
identities and credentials. These parameters may be optional or
mandatory and will be used for dynamically configuring devices
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that initialize in a network without any pre-configuration.
o Each profile MUST clearly identify if it may contain any sensitive
data. Such profiles MUST also identify the data elements that are
considered sensitive, i.e., data that cannot be compromised. As
an example, a device profile definition may identify itself as
containing sensitive data and indicate data such as device
credentials to be sensitive.
o When the device receives multiple profiles, the contents of each
profile type SHOULD only contain data relevant to the entity it
represents. As an example, consider a device that obtains all the
defined profiles. Information pertaining to the local network is
contained in the 'local-network' profile and not the 'user'
profile. This does not preclude relevant data about a different
entity from being included in a profile type, e.g., the 'device'
profile type may contain information about the users allowed to
access services via the device. A profile may also contain
starting information to obtain subsequent Profiles.
o Data overlap SHOULD be avoided across profile types, unless
necessary. If data overlap is present, prioritization of the data
is left to data definitions. As an example, the device profile
may contain the list of codecs to be used by the device and the
user Profile (for a user on the device) may contain the codecs
preferred by the user. Thus, the same data (usable codecs) is
present in two profiles. However, the data definitions may
indicate that to function effectively, any codec chosen for
communication needs to be present in both the profiles.
6.3.4. Profile Data Frameworks
The framework specified in this document does not address profile
data representation, storage or retrieval protocols. It assumes that
the PDS has a PCC based on existing or other Profile Data Frameworks.
While this framework does not impose specific constraints on any such
framework, it does allow for the propagation of profile content to
the PDS (specifically the PCC) from a network element or the device.
Thus, Profile Data or Retrieval frameworks used in conjunction with
this framework MAY consider techniques for propagating incremental,
atomic changes to the PDS. One means for propagating changes to a
PDS is defined in XCAP ([RFC4825]).
6.3.5. Additional Profile Types
This document specifies three profile types: local-network, device
and user. However, there may be use cases for additional profile
types. e.g., profile types for application specific profile data or
to provide enterprise-specific policies. Definition of such
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additional profile types is not prohibited, but considered out of
scope for this document. Such profile definitions MUST specify the
order of retrieval with respect to all the other profiles such as the
local-network, device and user profile types defined in this
document.
6.3.6. Deployment considerations
The framework defined in this document was designed to address
various deployment considerations, some of which are highlighted
below.
Provider relationships:
o The local network provider and the SIP service provider can often
be different entities, with no administrative or business
relationship with each other.
o There may be multiple SIP service providers involved, one for each
service that a user subscribes to (telephony service, instant
messaging, etc.); this Framework does not specify explicit
behavior in such a scenario, but it does not prohibit its usage
either.
o Each user accessing services via the same device may subscribe to
different sets of services, from different Service Providers.
User-device relationship:
o The relationship between devices and users can be many-to-many
(e.g., a particular device may allow for many users to obtain
subscription services through it, and individual users may have
access to multiple devices).
o Each user may have different preferences for use of services, and
presentation of those services in the device user interface.
o Each user may have different personal information applicable to
use of the device, either as related to particular services, or
independent of them.
7. Event Package Definition
The framework specified in this document proposes and specifies a new
SIP Event Package as allowed by [RFC3265]. The purpose is to allow
for devices to subscribe to specific profile types with PDSs and for
the PDSs to notify the devices with the profile data or content
indirection information.
The requirements specified in [RFC3265] apply to this package. The
following sub-sections specify the Event Package description and the
associated requirements. The framework requirements are defined in
Section 6.
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7.1. Event Package Name
The name of this package is "ua-profile". This value appears in the
Event header field present in SUBSCRIBE and NOTIFY requests for this
package as defined in [RFC3265].
7.2. Event Package Parameters
This package defines the following new parameters for the event
header:
"profile-type", "vendor", "model", "version", and "effective-by"
The following rules apply:
o All the new parameters, with the exception of the "effective-by"
parameter MUST only be used in SUBSCRIBE requests and ignored if
they appear in NOTIFY requests.
o The "effective-by" parameter is for use in NOTIFY requests only
and MUST be ignored if it appears in SUBSCRIBE requests.
The semantics of these new parameters are specified in the following
sub-sections.
7.2.1. profile-type
The "profile-type" parameter is used to indicate the token name of
the profile type the user agent wishes to obtain data or URIs for and
to be notified of subsequent changes. This document defines three
logical types of profiles and their token names. They are as
follows:
local-network: Specifying "local-network" type profile indicates the
desire for profile data (URI when content indirection is used)
specific to the local network.
device: Specifying "device" type profile(s) indicates the desire for
the profile data (URI when content indirection is used) and change
notification of the contents of the profile that is specific to
the device or user agent.
user: Specifying "user" type profile indicates the desire for the
profile data (URI when content indirection is used) and change
notification of the profile content for the user.
The "profile-type" is identified is identified in the Event header
parameter: profile-type. A separate SUBSCRIBE dialog is used for
each profile type. The profile type associated with the dialog can
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then be used to infer which profile type changed and is contained in
the NOTIFY or content indirection URI. The Accept header of the
SUBSCRIBE request MUST include the MIME types for all profile content
types for which the subscribing user agent wishes to retrieve
profiles or receive change notifications.
In the following syntax definition using ABNF, EQUAL and token are
defined in [RFC3261]. It is to be noted that additional profile
types may be defined in subsequent documents.
Profile-type = "profile-type" EQUAL profile-value
profile-value = profile-types / token
profile-types = "device" / "user" / "local-network"
The "device", "user" or "local-network" token in the profile-type
parameter may represent a class or set of profile properties.
Follow-on standards defining specific profile contents may find it
desirable to define additional tokens for the profile-type parameter.
Also additional content types may be defined along with the profile
formats that can be used in the Accept header of the SUBSCRIBE to
filter or indicate what data sets of the profile are desired.
7.2.2. vendor, model and version
The "vendor", "model" and "version" parameter values are tokens
specified by the implementer of the user agent. These parameters
MUST be provided in the SUBSCRIBE request for all profile types. The
implementer SHOULD use their DNS domain name (e.g., example.com) as
the value of the "vendor" parameter so that it is known to be unique.
These parameters are useful to the PDS to affect the profiles
provided. In some scenarios it is desirable to provide different
profiles based upon these parameters. e.g., feature property X in a
profile may work differently on two versions of the same user agent.
This gives the PDS the ability to compensate for or take advantage of
the differences. In the following ABNF defining the syntax, EQUAL
and quoted-string are defined in [RFC3261].
Vendor = "vendor" EQUAL quoted-string
Model = "model" EQUAL quoted-string
Version = "version" EQUAL quoted-string
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7.2.3. effective-by parameter
The "effective-by" parameter in the Event header of the NOTIFY
request specifies the maximum number of seconds before the user agent
must attempt to make the new profile effective. The "effective-by"
parameter MAY be provided in the NOTIFY request for any of the
profile types. A value of 0 (zero) indicates that the subscribing
user agent must attempt to make the profiles effective immediately
(despite possible service interruptions). This gives the PDS the
power to control when the profile is effective. This may be
important to resolve an emergency problem or disable a user agent
immediately. The "effective-by" parameter is ignored in all messages
other than the NOTIFY request. In the following ABNF, EQUAL and
DIGIT are defined in [RFC3261].
Effective-By = "effective-by" EQUAL 1*DIGIT
7.2.4. Summary of event parameters
The following are example Event headers which may occur in SUBSCRIBE
requests. These examples are not intended to be complete SUBSCRIBE
requests.
Event: ua-profile;profile-type=device;
vendor="vendor.example.com";model="Z100";version="1.2.3"
Event: ua-profile;profile-type=user;
vendor="premier.example.com";model="trs8000";version="5.5"
The following are example Event headers which may occur in NOTIFY
requests. These example headers are not intended to be complete
SUBSCRIBE requests.
Event: ua-profile;effective-by=0
Event: ua-profile;effective-by=3600
The following table shows the use of Event header parameters in
SUBSCRIBE requests for the three profile types:
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profile-type || device | user | local-network
=============================================
vendor || m | m | m
model || m | m | m
version || m | m | m
effective-by || | |
m - mandatory
s - SHOULD be provided
o - optional
Non-specified means that the parameter has no meaning and should be
ignored.
The following table shows the use of Event header parameters in
NOTIFY requests for the three profile types:
profile-type || device | user | local-network
=============================================
vendor || | |
model || | |
version || | |
effective-by || o | o | o
7.3. SUBSCRIBE Bodies
This package defines no use of the SUBSCRIBE request body. If
present, it MUST be ignored.
Future enhancements to the framework may specify a use for the
SUBSCRIBE request body (e.g., mechanisms using etags to minimize
Profile Notifications to devices with current profile versions).
7.4. Subscription Duration
The duration of a subscription is specific to SIP deployments and no
specific recommendation is made by this Event Package. If absent, a
value of 86400 seconds (24 hours; 1 day) is RECOMMENDED since the
presence (or absence) of a device subscription is not time critical
to the regular functioning of the PDS.
It is to be noted that a one-time fetch of a profile can be
accomplished by setting the 'Expires' parameter to a value of Zero,
as specified in [RFC3265].
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7.5. NOTIFY Bodies
The framework specifying the Event Package allows for the NOTIFY body
to contain the profile data or a pointer to the profile data using
content indirection. The framework does not define any profile data
and delegates specification of utilized MIME types Profile Data
Frameworks. For profile data delivered via content indirection, the
following apply:
o The Content-ID MIME header, as described in [RFC4483] MUST be used
for each Profile document URI.
o At a minimum, the "http:" and "https:" URI schemes MUST be
supported; other URI schemas MAY be supported based on the Profile
Data Frameworks (examples include FTP [RFC0959], HTTP [RFC2616],
HTTPS [RFC2818], LDAP [RFC4510] and XCAP [RFC4825] ).
The NOTIFY body SHOULD include a MIME type specified in the 'Accept'
header of the SUBSCRIBE. Further, if the Accept header of the
SUBSCRIBE included the MIME type message/external-body (indicating
support for content indirection) then the PDS MAY use content
indirection in the NOTIFY body for providing the profiles.
7.6. Notifier Processing of SUBSCRIBE Requests
A successful SUBSCRIBE request results in a NOTIFY with either
profile contents or a pointer to it (via Content Indirection). If
the NOTIFY is expected to contain profile contents or the Notifier is
unsure, the SUBSCRIBE SHOULD be either authenticated or transmitted
over an integrity protected SIP communication channels. Exceptions
to authenticating such SUBSCRIBEs include cases where the identity of
the Subscriber is unknown and the Notifier is configured to accept
such requests.
The Notifier MAY also authenticate SUBSCRIBE messages even if the
NOTIFY is expected to only contain a pointer to profile data.
Securing data sent via Content Indirection is covered in Section 10.
If the profile type indicated in the "profile-type" Event header
parameter is unavailable or the Notifier is configured not to provide
it, the Notifier SHOULD return a 404 response to the SUBSCRIBE
request. If the specific user or device is unknown, the Notifier MAY
either accept or reject the subscription.
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7.7. Notifier Generation of NOTIFY Requests
As specified in [RFC3265], the Notifier MUST always send a NOTIFY
request upon accepting a subscription. If the device or user is
unknown and the Notifier chooses to accept the subscription, the
Notifier MAY either respond with profile data (e.g., default profile
data) or provide no profile information (i.e. no body or content
indirection).
If the URI in the SUBSCRIBE request is a known identity and the
requested profile information is available (i.e. as specified in the
profile-type parameter of the Event header), the Notifier SHOULD send
a NOTIFY with profile data. Profile data MAY be sent as profile
contents or via Content Indirection (if the content indirection MIME
type was included in the Accept header). To allow for Content
Indirection, the Subscriber MUST support the "http:" or "https:" URI
schemas. If the Subscriber wishes to support alternative URI schemas
it MUST be indicated in the "schemes" Contact header field parameter
as defined in [RFC4483]. The Notifier MUST NOT use any schema that
was not indicated in the "schemas" Contact header field.
The Notifier MAY specify when the new profiles must be made effective
by the Subscriber by specifying a maximum time in seconds (zero or
more) in the "effective-by" event header parameter.
If the SUBSCRIBE was received over an integrity protected SIP
communications channel, the Notifier SHOULD send the NOTIFY over the
same channel.
7.8. Subscriber Processing of NOTIFY Requests
A Subscriber to this event package MUST adhere to the NOTIFY request
processing behavior specified in [RFC3265]. If the Notifier
indicated an effective time (using the "effective-by" Event Header
parameter), it SHOULD attempt to make the profiles effective within
the specified time. Exceptions include deployments that prohibit
such behavior in certain cases (e.g., emergency sessions are in
progress). When profile data cannot be applied within the
recommended timeframe and this affects device behavior, any actions
to be taken SHOULD be defined by the profile data definitions. By
default, the Subscriber is RECOMMENDED to make the profiles effective
as soon as possible.
The Subscriber MUST always support "http:" or "https:" and be
prepared to accept NOTIFY messages with those URI schemas.The
subscriber MUST also be prepared to receive a NOTIFY request with no
body. The subscriber MUST NOT reject the NOTIFY request with no
body. The subscription dialog MUST NOT be terminated by a NOTIFY
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with no body.
7.9. Handling of Forked Requests
This Event package allows the creation of only one dialog as a result
of an initial SUBSCRIBE request as described in section 4.4.9 of
[RFC3265]. It does not support the creation of multiple
subscriptions using forked SUBSCRIBE requests.
7.10. Rate of Notifications
The rate of notifications for the profiles in this framework is
deployment specific, but expected to be infrequent. Hence, the Event
Package specification does not specify a throttling or minimum period
between NOTIFY requests
7.11. State Agents
State agents are not applicable to this Event Package.
8. Examples
This section provides examples along with sample SIP message bodies
relevant to this framework. Both the examples are derived from a
snapshot of Section 5.1, specifically the request for the device
profile. The examples are purely informative and in case of
conflicts with the framework or protocols used for illustration, the
latter should be deemed normative.
8.1. Example 1: Device requesting profile
This example illustrates the detailed message flows between the
device and the SIP Service Provider's network for requesting and
retrieving the profile (the flow uses the device profile as an
example).
The following are assumed for this example:
o Device is assumed to have established local network connectivity;
NAT and Firewall considerations are assumed to have been addressed
by the SIP Service Provider.
o Examples are snapshots only and do not illustrate all the
interactions between the device and the Service Provider's network
(and none between the entities in the SIP Service Provider's
network).
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o All SIP communication with the SIP Service Provider happens via a
SIP Proxy.
o HTTP over TLS is assumed to be the Profile Data method used (any
suitable alternative can be used as well).
The flow diagram and an explanation of the messages follow.
+----------------------+
+--------+ | SIP Service Provider |
| Device | | |
|(SIP UA)| | SIP PDS HTTP |
+--------+ | PROXY Server |
| |
+----------------------+
| | | |
| | | |
| SUBSCRIBE | | |
(SReq)|--------device profile--------->| | |
| |------>| |
| |200 OK | |
| 200 OK |<------| |
(SRes)|<-------------------------------| | |
| | | |
| | NOTIFY| |
| NOTIFY (Content Indirection)|<------| |
(NTFY)|<-------------------------------| | |
| 200 OK | | |
(NRes)|------------------------------->|200 OK | |
| |------>| |
| |
| |
| |
|<<<<<<<<<<<<< TLS establishment >>>>>>>>>>>>>|
| |
| HTTP Request |
(XReq)|---------------------------------------------->|
| |
| HTTP Response |
(XRes)|<----------------------------------------------|
| |
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(SReq)
the device transmits a request for the 'device' profile using the
SIP SUBSCRIBE utilizing the Event Package specified in this
framework.
* Note: Some of the header fields (e.g., SUBSCRIBE, Event, via)
are continued on a separate line due to format constraints of
this document.
SUBSCRIBE sip:urn%3auuid%3a00000000-0000-1000-0000-00FF8D82EDCB
@example.com SIP/2.0
Event: ua-profile;profile-type=device;vendor="vendor.example.net";
model="Z100";version="1.2.3";
From: sip:urn%3auuid%3a00000000-0000-1000-0000-00FF8D82EDCB
@example.com;tag=1234
To: sip:urn%3auuid%3a00000000-0000-1000-0000-00FF8D82EDCB@example.com
Call-ID: 3573853342923422@192.0.2.44
CSeq: 2131 SUBSCRIBE
Contact: sip:urn%3auuid%3a00000000-0000-1000-0000-00FF8D82EDCB
@example.com
;+sip.instance="<urn:uuid:00000000-0000-0000-0000-123456789AB0>"
Via: SIP/2.0/TCP 192.0.2.41;
branch=z9hG4bK6d6d35b6e2a203104d97211a3d18f57a
Accept: message/external-body, application/x-z100-device-profile
Content-Length: 0
(SRes)
the SUBSCRIBE request is received by a SIP Proxy in the Service
Provider's network which transmits it to the PDS. The PDS accepts
the response and responds with a 200 OK
* Note: The device and the SIP proxy may have established a
secure communications channel (e.g., TLS).
(NTFY)
subsequently, the PDS transmits a SIP NOTIFY message indicating
the profile location
* Note: Some of the fields (e.g., content-type) are continued on
a separate line due to format constraints of this document.
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NOTIFY sip:urn%3auuid%3a00000000-0000-1000-0000-00FF8D82EDCB
@192.0.2.44 SIP/2.0
Event: ua-profile;effective-by=3600
From: sip:urn%3auuid%3a00000000-0000-1000-0000-00FF8D82EDCB@example.com
;tag=abca
To: sip:urn%3auuid%3a00000000-0000-1000-0000-00FF8D82EDCB@example.com
;tag=1231
Call-ID: 3573853342923422@192.0.2.44
CSeq: 322 NOTIFY
Via: SIP/2.0/UDP 192.0.2.3;
branch=z9hG4bK1e3effada91dc37fd5a0c95cbf6767d0
MIME-Version: 1.0
Content-Type: message/external-body; access-type="URL";
expiration="Mon, 01 Jan 2010 09:00:00 UTC";
URL="http://example.com/z100-000000000000.html";
size=9999;
hash=10AB568E91245681AC1B
Content-Type: application/x-z100-device-profile
Content-ID: <39EHF78SA@example.com>
.
.
.
(NRes)
Device accepts the NOTIFY message and responds with a 200 OK
(XReq)
once the necessary secure communications channel is established,
the device sends an HTTP request to the HTTP server indicated in
the NOTIFY
(XRes)
the HTTP server responds to the request via a HTTP response
containing the profile contents
8.2. Example 2: Device obtaining change notification
The following example illustrates the case where a user (X) is
simultaneously accessing services via two different devices (e.g.,
Multimedia entities on a PC and PDA) and has access to a user
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Interface (UI) that allows for changes to the user profile.
The following are assumed for this example:
o The devices (A & B) obtain the necessary profiles from the same
SIP Service Provider.
o The SIP Service Provider also provides a user Interface (UI) that
allows the user to change preferences that impact the user
profile.
The flow diagram and an explanation of the messages follow.
o Note: The example only shows retrieval of user X's profile, but it
may request and retrieve other profiles (e.g., local-network,
Device).
----- -----
|User |_________| UI* | * = User Interface
| X | | |
----- -----
/ \
/ \
/ \ +----------------------+
+--------+ +--------+ | SIP Service Provider |
| Device | | Device | | |
| A | | B | | SIP PDS HTTP |
+--------+ +--------+ | PROXY Server |
+----------------------+
| | | |
| | | |
(A-EX)|<=Enrolls for User X's profile=>|<=====>| |
| | | |
| |
(A-RX)|<===Retrieves User X's profile================>|
| |
| | | | |
| | Enrolls for | | |
| (B-EX)|<== User X's ==>|<=====>| |
| | profile | | |
| | | | |
| | |
| (B-RX)|<= Retrieves User X's profile=>|
| |
| | |
| (HPut)|---------------------->|
| | |
| (HRes)|<----------------------|
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| |
| | | |
| | NOTIFY| |
| NOTIFY |<------| |
(A-NT)|<-------------------------------| | |
| 200 OK | | |
(A-RS)|------------------------------->|200 OK | |
| |------>| |
| |
| | | NOTIFY| |
| | NOTIFY |<------| |
| (B-NT)|<---------------| | |
| | 200 OK | | |
| (B-RS)|--------------->|200 OK | |
| | |------>| |
| |
| |
(A-RX)|<===Retrieves User X's profile================>|
| |
| | |
| | |
| (B-RX)|<= Retrieves User X's profile=>|
| | |
(A-EX) Device A discovers, enrolls and obtains notification related
to user X's profile.
(A-RX) Device A retrieves user X's profile.
(B-EX) Device B discovers, enrolls and obtains notification related
to user X's profile.
(B-RX) Device B retrieves user X's profile.
(HPut) Changes affected by the user via the user Interface (UI) are
uploaded to the HTTP Server.
* Note: The UI itself can act as a device and subscribe to user
X's profile. This is not the case in the example shown.
(HRes) Changes are accepted by the HTTP server.
(A-NT) PDS transmits a NOTIFY message to device A indicating the
changed profile. A sample message is shown below:
Note: Some of the fields (e.g., Via) are continued on a
separate line due to format constraints of this document.
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NOTIFY sip:userX@192.0.2.44 SIP/2.0
Event: ua-profile;effective-by=3600
From: sip:userX@sip.example.net;tag=abcd
To: sip:userX@sip.example.net.net;tag=1234
Call-ID: 3573853342923422@192.0.2.44
CSeq: 322 NOTIFY
Via: SIP/2.0/UDP 192.0.2.3;
branch=z9hG4bK1e3effada91dc37fd5a0c95cbf6767d1
MIME-Version: 1.0
Content-Type: message/external-body; access-type="URL";
expiration="Mon, 01 Jan 2010 09:00:00 UTC";
URL="http://www.example.com/user-x-profile.html";
size=9999;
hash=123456789AAABBBCCCDD
.
.
.
(A-RS) Device A accepts the NOTIFY and sends a 200 OK
(B-NT) PDS transmits a NOTIFY message to device B indicating the
changed profile. A sample message is shown below:
Note: Some of the fields (e.g., Via) are continued on a
separate line due to format constraints of this document.
NOTIFY sip:userX@192.0.2.43 SIP/2.0
Event: ua-profile;effective-by=3600
From: sip:userX@sip.example.net;tag=abce
To: sip:userX@sip.example.net.net;tag=1235
Call-ID: 3573853342923422@192.0.2.43
CSeq: 322 NOTIFY
Via: SIP/2.0/UDP 192.0.2.3;
branch=z9hG4bK1e3effada91dc37fd5a0c95cbf6767d2
MIME-Version: 1.0
Content-Type: message/external-body; access-type="URL";
expiration="Mon, 01 Jan 2010 09:00:00 UTC";
URL="http://www.example.com/user-x-profile.html";
size=9999;
hash=123456789AAABBBCCCDD
.
.
.
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(B-RS) Device B accepts the NOTIFY and sends a 200 OK
(A-RX) Device A retrieves the updated profile pertaining to user X
(B-RX) Device B retrieves the updated profile pertaining to user X
9. IANA Considerations
There are two IANA considerations associated with this document, SIP
Event Package and SIP configuration profile types. These are
outlined in the following sub-sections.
9.1. SIP Event Package
This specification registers a new event package as defined in
[RFC3265]. The following information required for this registration:
Package Name: ua-profile
Package or Template-Package: This is a package
Published Document: RFC XXXX (Note to RFC Editor: Please fill in
XXXX with the RFC number of this specification)
Persons to Contact: Daniel Petrie dan.ietf AT SIPez DOT com,
sumanth@cablelabs.com
New event header parameters: profile-type, vendor, model, version,
effective-by (the profile-type parameter has predefined values.
The new event header parameters do not)
The following table illustrates the additions to the IANA SIP Header
Field Parameters and Parameter Values: (Note to RFC Editor: Please
fill in XXXX with the RFC number of this specification)
Predefined
Header Field Parameter Name Values Reference
---------------------------- --------------- --------- ---------
Event profile-type Yes [RFCXXXX]
Event vendor No [RFCXXXX]
Event model No [RFCXXXX]
Event version No [RFCXXXX]
Event effective-by No [RFCXXXX]
9.2. Registry of SIP configuration profile types
This document requests IANA to register new SIP configuration profile
types at http://www.iana.org/assignments/sip-parameters under "SIP
Configuration Profile Types".
SIP configuration profile types allocations fall under the category
"Specification Required", as explained in "Guidelines for Writing an
IANA Considerations Section in RFCs" ([RFC2434]).
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Registrations with the IANA MUST include a the profile type, and a
published document which describes its purpose and usage.
As this document specifies three SIP configuration profile types, the
initial IANA registration will contain the information shown in the
table below. It also demonstrates the type of information maintained
by the IANA.
Profile Type Reference
-------------- ---------
local-network [RFCXXXX]
device [RFCXXXX]
user [RFCXXXX]
CONTACT:
-------
sumanth@cablelabs.com
Daniel Petrie dan.ietf AT SIPez DOT com
Note to RFC editor: Please replace RFCXXXX with the RFC number
assigned to this document.
10. Security Considerations
The framework specified in this document enables profile data
delivery to devices. It specifies profile delivery stages, an event
package and several profile types.
There are three stages: Enrollment, Content Retrieval, and Change
Notification.
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+------+ +-----+
| | | |
|Device| | PNC |
| | | |
+------+ +-----+
| |
| Profile Enrollment |
|---------------------->|
| |
| Initial Notification |
|<----------------------|
| |
+------+ +-----+
| | | |
|Device| | PNC |
| | | |
+------+ +-----+
| |
| Profile Enrollment |
|---------------------->|
| |
| Change Notification |
|<----------------------|
| |
+------+ +-----+
| | | |
|Device| | PCC |
| | | |
+------+ +-----+
| |
| Profile Request | (When content
|---------------------->| indirection
| | is used)
| Profile Response |
|<----------------------|
| |
PNC = Profile Notification Component
PCC = Profile Content Component
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Figure 23: Profile Delivery Stages
Enrollment allows a device to request a profile. To transmit the
request the device relies on cached, configured or discovered data.
Such data includes provider domain names, identities, and
credentials. The device uses [RFC3263] to discover the next-hop SIP
entity which can be a SIP proxy or the PDS. It then transmits the
request, after establishing a TLS session if required. If obtained
via a SIP proxy, the Request-URI is used to route it to a PDS (via an
authoritative SIP proxy, if required).
When a PDS receives the enrollment request, it can either challenge
the presented identity (if any) or admit the enrollment.
Authorization then decides if the enrollment is accepted. If
accepted, the PDS sends an initial notification that contains either:
profile data or content indirection information. The profile data
can contain information specific to an entity (such as the device or
a user) and may contain sensitive information (such as credentials).
Compromise of such data can lead to threats such as impersonation
attacks (establishing rogue sessions), theft of service (if services
are obtainable), and zombie attacks. Even if the profile data is
provided using content indirection, PCC information within the
notification can lead to threats such as denial of service attacks
(rogue devices bombard the PCC with requests for a specific profile)
and attempts to modify erroneous data onto the PCC (since the
location and format may be known). It is also important for the
device to ensure the authenticity of the PNC since impersonation of
the SIP service provider can lead to Denial of Service, Man-in-the-
Middle attacks, etc.
Profile content retrieval allows a device to retrieve profile data
from a PCC. This communication is accomplished using one of many
profile delivery protocols or frameworks, such as HTTP or HTTPS as
specified in this document. However, since the profile data returned
is subject to the same considerations as that sent via profile
notification, the same threats exist.
Profile-specific considerations follow.
10.1. Local-network profile
A local network may or may not (e.g., home router) support local-
network profiles as specified in this framework. Even if supported,
the PDS may only be configured with a generic local-network profile
that is provided to every device capable of accessing the network.
Such a PDS may not implement any authentication requirements or TLS.
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Alternatively, certain deployments may require the entities - device
and the PDS - to mutually authenticate prior to profile enrollment.
Such networks may pre-configure user identities to the devices and
allow user-specific local-network profiles. In such networks the PDS
will contain X.509 certificates and support TLS, and the devices are
pre-configured with user identities, credentials and implement TLS.
This framework supports both use cases and variations in-between.
However, devices obtaining local-network profiles from an
unauthenticated PDS are cautioned against potential MiM or PDS
impersonation attacks. This framework requires that a device reject
sensitive data, such as credentials, from unauthenticated local-
network sources (exceptions are noted). It also prohibits devices
from responding to authentication challenges from unauthenticated
PDSs. Responding to unauthenticated challenges allows for dictionary
attacks that can reveal weak passwords.
If deployments prefer devices to obtain profiles only from pre-
configured domains (e.g., partner networks), they MAY require such
devices to establish TLS prior to obtaining the local-network
profile.
The use of SIP Identity is useful in cases when TLS is not used but
the device still obtains a profile (e.g., the local-network profile).
In such cases the device provider, or the user, can use the SIP
Identity header to verify the source of the local-network profile.
However, the presence of the header does not guarantee the validity
of the data. It verifies the source and confirms data integrity, but
the data obtained from an undesired source may still be invalid
(e.g., it can be invalid or contain malicious content).
10.2. Device profile
Device profiles deal with device-specific configuration. They may be
provided to unknown devices that are attempting to obtaining profiles
for purposes of trials and self-subscription to SIP services (not to
be confused with [RFC3265]), emergency services
([I-D.ietf-ecrit-phonebcp]), or to devices that are known by the PDS.
Devices that are not aware of any device providers (i.e., no cached
or configured information) will have to discover a PDS in the network
they connect to. In such a case the discovered information may lead
them to a PDS that provides enough profile data to enable device
operation. This configuration can also provide a user AoR that can
be used in the local-network and credentials (temporary or long-term)
that will be used for future communication with the network. This
may enable the device to communicate with a device provider who
allows for self-subscription (e.g., web interface, interactive voice
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response or customer service representative). It may also allow the
device a choice of device providers and allow the end-user to choose
one. It is to be noted that such devices are at the mercy of the
network they connect to initially. If they are initialized in a
rogue network, or get hijacked by a rogue PDS, the end-user may be
left without desired device operation, or worse unwanted operation.
To mitigate such factors the device provider may communicate
temporary credentials (PINs that can be entered via an interface) or
permanent credentials (e.g., a USB device) to the end-user for
connectivity. If such methods are used the large-entropy credentials
MUST be used, or quickly replaced with such, to minimize the impact
of dictionary attacks. Future enhancements to this framework may
specify device capabilities that allow for mutual authentication
without pre-configuration (e.g., X.509 certificates using PKI).
Once a device is associated with a device provider (either
dynamically or via pre-configuration using a user interface or prior
to distribution), the device profile is vital to device operation.
This is because the device profile can contain important operational
information such as users that are to be allowed access (white-list
or black-list), user credentials (if required) and other sensitive
information. Thus, it is also necessary to ensure that the device
profile is not obtained via an unauthenticated source or tampered
during transit. Thus the framework requires that devices supporting
any sensitive device profiles establish next-hop authenticated TLS
connections prior to device enrollment. However, given the
importance of the device profile it also allows for profile requests
in cases where the PDS does not implement TLS. It also allows the
PDSs to perform authentication without requiring TLS. However, this
leaves the communication open to MiM attacks and SHOULD be avoided.
Additionally any credential used SHOULD be of sufficiently large-
entropy to prevent dictionary attacks. Devices SHOULD use the
'cnonce' parameter ([RFC2617]) to thwart "offline" dictionary
attacks.
10.3. User profile
Devices can only request user profiles for users that are known by a
SIP service provider. Thus, PDSs are prohibited from accepting user
profile enrollment requests for users that are unknown in the
network. If the user AoR is a SIPS URI then the device is required
to establish a next-hop authenticated TLS session. This framework
RECOMMENDS this for profiles with sensitive data. If it is a SIP
URI, then the device is still recommended to attempt TLS
establishment to ensure protection against rogue PDSs. A PDS is
always recommended to authenticate the user AoR prior to profile
enrollment. The considerations are the same as that for a device
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profile with pre-configured user AoR.
11. Acknowledgements
The author appreciates all those who contributed and commented on the
many iterations of this document. Detailed comments were provided by
the following individuals: Jonathan Rosenberg from Cisco, Henning
Schulzrinne from Columbia University, Cullen Jennings from Cisco,
Rohan Mahy from Plantronics, Rich Schaaf from Pingtel, Volker Hilt
from Bell Labs, Adam Roach of Estacado Systems, Hisham Khartabil from
Telio, Henry Sinnreich from MCI, Martin Dolly from AT&T Labs, John
Elwell from Siemens, Elliot Eichen and Robert Liao from Verizon, Dale
Worley from Pingtel, Francois Audet from Nortel, Roni Even from
Polycom, Jason Fischl from Counterpath, Josh Littlefield from Cisco,
Nhut Nguyen from Samsung.
The final revisions of this document were a product of design team
discussions. The editor wishes to extend special appreciation to the
following design team members for their numerous reviews and specific
contributions to various sections: Josh Littlefield from Cisco
(Executive Summary, Overview, Section 6), Peter Blatherwick from
Mitel (Section 6), Cullen Jennings (Security), Sam Ganesan (Section
6) and Mary Barnes (layout, Section 6).
The following design team members are thanked for numerous reviews
and general contributions: Martin Dolly from AT&T Labs, Jason Fischl
from Counterpath, Alvin Jiang of Engin and Francois Audet from
Nortel.
The following SIPPING WG members are thanked for numerours reviews,
comments and recommendations: John Elwell from Siemens, Donald Lukacs
from Telcordia, and Eugene Nechamkin from Broadcom.
Additionally, sincere appreciation is extended to the chairs (Mary
Barnes from Nortel and Gonzalo Camarillo from Ericsson) and the Area
Directors (Cullen Jennings from Cisco and Jon Peterson from Neustar)
for facilitating discussions, reviews and contributions. The editor
would also like to extend a special thanks to the comments and
recommendations provided by the SIPPING WG, specifically Keith Drage
from Lucent (restructuring proposal).
12. Change History
[[RFC Editor: Please remove this entire section upon publication as
an RFC.]]
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12.1. Changes from draft-ietf-sipping-config-framework-11.txt
The following are the major changes that have been incorporated into
this I-D.
o Incorporated the decisions taken at the last IETF: added an
executive summary section; removed 'device-id' and replaced with
'sip.instance'
o Removed the HTTPS bootstrapping section (this could be a different
I-D)
o Added IANA registry for the 'profile-type' parameter (comment from
Adam Roach)
o Incorporated comments from Cullen Jennings, John Elwell, and
design team reviews
o Revised section 6 to make it flow better
o Removed 'Profile Change Modification' from the document
o Revised the security section.
12.2. Changes from draft-ietf-sipping-config-framework-10.txt
The following are the changes that have been incorporated into this
I-D, resulting from the design team discussions based on Working
Group feedback.
o Modified the "From" header of the local network profile to reflect
the user's AoR, if any; delegated the device identifier to a new
event header termed "device-id"; removed use for 'network-user'
within the local-network profile; if there are objections to this,
please educate us!
o Added text to indicate DHCPv4 or DHCPv6 to accomodate IPv4 and
IPv6 environments
o Replaced generic 'Service Provider' with terms to better represent
scenarios
o Analyzed the current SHOULD v/s MUST requirements for the Profile
Framework and made modifications
o Referenced RFC4122 instead of OUTBOUND
o Simplified the introductory sections to better illustrate
potential deployment possibilities; indicated the minimum profile
supported to be 'device'
o Revamped the security considerations sections
12.3. Changes from draft-ietf-sipping-config-framework-09.txt
Following the ad-hoc SIPPING WG discussions at IETF#67 and as per the
email from Gonzalo Camarillo dated 12/07/2006, Sumanth was appointed
as the new editor. This sub-section highlights the changes made by
the editor (as per expert recommendations from the SIPPING WG folks
interested in this effort) and the author.
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Changes incorporated by the editor:
o Document was restructured based on a) Keith's recommendations in
the email dated 11/09/2006 and responses (Peter, Sumanth, Josh) b)
subsequent discussions by the ad-hoc group consisting of the
editor, the author, expert contributors (Peter Blatherwick, Josh
Littlefield, Alvin Jiang, Jason Fischl, Martin Dolly, Cullen
Jennings) and the co-chairs . Further changes follow.
o Use cases were made high-level with detailed examples added later
on
o Several sections were modified as part of the restructuring (e.g.,
Overview, Introduction, Framework Requirements, Security Sections)
o General editorial updates were made
Changes incorporated by the author:
o Incorporated numerous edits and corrections from CableLabs review.
o Used better ascii art picture of overview from Josh Littlefield
o Fixed the normative text for network-user so that it is now
consistant: MAY provide for device profile, MUST provide for
local-network profile.
12.4. Changes from draft-ietf-sipping-config-framework-08.txt
The Request URI for profile-type=localnet now SHOULD not have a
user part to make routing easier. The From field SHOULD now
contain the device id so that device tracking can still be done.
Described the concept of profile-type as a filter and added
normative text requiring 404 for profile types not provided.
Moved "application" profile type to
draft-ietf-sipping-xcap-config-01. The "application" value for
the profile-type parameter will also be used as a requirement that
XCAP be supported.
Fixed text on certificate validation.
Added new HTTP header: Event to IANA section and clean up the IANA
section.
Added diagram for Service Provider use case schenario.
Added clarification for HTTP Event header.
Added clarification of subscriber handling of NOTIFY with no body.
12.5. Changes from draft-ietf-sipping-config-framework-07.txt
Made XCAP informative reference. Removed "document" and "auid"
event header parameters, and Usage of XCAP section to be put in
separate supplementary draft.
Fixed ABNF for device-id to be addr-spec only (not name-addr) and
to be quoted as well.
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Synchronized with XCAP path terminology. Removed XCAP path
definition as it is already defined in XCAP.
User agent instance ID is now defined in output (not GRUU).
Clarified the rational for the device-id parameter.
Added text to suggest URIs for To and From fields.
Clarified use of device-id parameter.
Allow the use of the auid and document parameters per request by
the OMA.
12.6. Changes from draft-ietf-sipping-config-framework-06.txt
Restructured the introduction and overview section to be more
consistent with other Internet-Drafts.
Added additional clarification for the Digest Authentication and
Certificate based authentication cases in the security section.
Added two use case scenarios with cross referencing to better
illustrate how the framework works. Added better cross
referencing in the overview section to help readers find where
concepts and functionality is defined in the document.
Clarified the section on the use of XCAP. Changed the Event
parameter "App-Id" to "auid". Made "auid" mutually exclusive to
"document". "auid" is now only used with XCAP.
Local network subscription URI changed to <device-id>@
<local-network> (was anonymous@<local-network>). Having a
different Request URI for each device allows the network
management to track user agents and potentially manage bandwidth,
port allocation, etc.
Changed event package name from sip-profile to ua-profile per
discussion on the list and last IETF meeting.
Changed "local" profile type token to "local-network" per
discussion on the list and last IETF meeting.
Simplified "Vendor", "Model", "Version" event header parameters to
allow only quoted string values (previously allowed token as
well).
Clarified use of the term cache.
Added references for ABNF constructs.
Numerous editorial changes. Thanks Dale!
12.7. Changes from draft-ietf-sipping-config-framework-05.txt
Made HTTP and HTTPS profile transport schemes mandatory in the
profile delivery server. The subscribing device must implement
HTTP or HTTPS as the profile transport scheme.
Rewrote the security considerations section.
Divided references into Normative and Informative.
Minor edits throughout.
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12.8. Changes from draft-ietf-sipping-config-framework-04.txt
Clarified usage of instance-id
Specify which event header parameters are mandatory or optional
and in which messages.
Included complete list of event header parameters in parameter
overview and IANA sections.
Removed TFTP reference as protocol for profile transport.
Added examples for discovery.
Added ABNF for all event header parameters.
Changed profile-name parameter back to profile-type. This was
changed to profile-name in 02 when the parameter could contain
either a token or a path. Now that the path is contained in the
separate parameter: "document", profile-type make more sense as
the parameter name.
Fixed some statements that should have and should not have been
normative.
Added the ability for the user agent to request that the default
user associated with the device be set/changed using the
"device-id" parameter.
A bunch of editorial nits and fixes.
12.9. Changes from draft-ietf-sipping-config-framework-03.txt
Incorporated changes to better support the requirements for the use
of this event package with XCAP and SIMPLE so that we can have one
package (i.e. simple-xcap-diff now defines a content type not a
package). Added an additional profile type: "application". Added
document and app-id Event header parameters in support of the
application profile. Define a loose high level data model or
relationship between the four profile types. Tried to edit and fix
the confusing and ambiguous sections related to URI formation and
discovery for the different profile types. Better describe the
importance of uniqueness for the instance id which is used in the
user part of the device URI.
12.10. Changes from draft-ietf-sipping-config-framework-02.txt
Added the concept of the local network as a source of profile data.
There are now three separate logical sources for profile data: user,
device and local network. Each of these requires a separate
subscription to obtain.
12.11. Changes from draft-ietf-sipping-config-framework-01.txt
Changed the name of the profile-type event parameter to profile-name.
Also allow the profile-name parameter to be either a token or an
explicit URI.
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Allow content indirection to be optional. Clarified the use of the
Accept header to indicate how the profile is to be delivered.
Added some content to the Iana section.
12.12. Changes from draft-ietf-sipping-config-framework-00.txt
This version of the document was entirely restructured and re-written
from the previous version as it had been micro edited too much.
All of the aspects of defining the event package are now organized in
one section and is believed to be complete and up to date with
[RFC3265].
The URI used to subscribe to the event package is now either the user
or device address or record.
The user agent information (vendor, model, MAC and serial number) are
now provided as event header parameters.
Added a mechanism to force profile changes to be make effective by
the user agent in a specified maximum period of time.
Changed the name of the event package from sip-config to ua-profile
Three high level security approaches are now specified.
12.13. Changes from draft-petrie-sipping-config-framework-00.txt
Changed name to reflect SIPPING work group item
Synchronized with changes to SIP DHCP [RFC3361], SIP [RFC3261] and
[RFC3263], SIP Events [RFC3265] and content indirection [RFC4483]
Moved the device identity parameters from the From field parameters
to user-agent header parameters.
Many thanks to Rich Schaaf of Pingtel, Cullen Jennings of Cisco and
Adam Roach of Estacado Systems for the great comments and input.
12.14. Changes from draft-petrie-sip-config-framework-01.txt
Changed the name as this belongs in the SIPPING work group.
Minor edits
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12.15. Changes from draft-petrie-sip-config-framework-00.txt
Split the enrollment into a single SUBSCRIBE dialog for each profile.
The 00 draft sent a single SUBSCRIBE listing all of the desired.
These have been split so that each enrollment can be routed
differently. As there is a concept of device specific and user
specific profiles, these may also be managed on separate servers.
For instance in a nomadic situation the device might get its profile
data from a local server which knows the LAN specific profile data.
At the same time the user specific profiles might come from the
user's home environment profile delivery server.
Removed the Config-Expires header as it is largely superfluous with
the SUBSCRIBE Expires header.
Eliminated some of the complexity in the discovery mechanism.
Suggest caching information discovered about a profile delivery
server to avoid an avalanche problem when a whole building full of
devices powers up.
Added the user-profile From header field parameter so that the device
can request a user specific profile for a user that is different from
the device's default user.
13. References
13.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 2434,
October 1998.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
Leach, P., Luotonen, A., and L. Stewart, "HTTP
Authentication: Basic and Digest Access Authentication",
RFC 2617, June 1999.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
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[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002.
[RFC3263] Rosenberg, J. and H. Schulzrinne, "Session Initiation
Protocol (SIP): Locating SIP Servers", RFC 3263,
June 2002.
[RFC3265] Roach, A., "Session Initiation Protocol (SIP)-Specific
Event Notification", RFC 3265, June 2002.
[RFC3319] Schulzrinne, H. and B. Volz, "Dynamic Host Configuration
Protocol (DHCPv6) Options for Session Initiation Protocol
(SIP) Servers", RFC 3319, July 2003.
[RFC3361] Schulzrinne, H., "Dynamic Host Configuration Protocol
(DHCP-for-IPv4) Option for Session Initiation Protocol
(SIP) Servers", RFC 3361, August 2002.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
July 2005.
[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.1", RFC 4346, April 2006.
[RFC4474] Peterson, J. and C. Jennings, "Enhancements for
Authenticated Identity Management in the Session
Initiation Protocol (SIP)", RFC 4474, August 2006.
[RFC4483] Burger, E., "A Mechanism for Content Indirection in
Session Initiation Protocol (SIP) Messages", RFC 4483,
May 2006.
[RFC4704] Volz, B., "The Dynamic Host Configuration Protocol for
IPv6 (DHCPv6) Client Fully Qualified Domain Name (FQDN)
Option", RFC 4704, October 2006.
13.2. Informative References
[I-D.ietf-ecrit-phonebcp]
Rosen, B. and J. Polk, "Best Current Practice for
Communications Services in support of Emergency Calling",
draft-ietf-ecrit-phonebcp-01 (work in progress),
March 2007.
[I-D.ietf-sip-outbound]
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Jennings, C. and R. Mahy, "Managing Client Initiated
Connections in the Session Initiation Protocol (SIP)",
draft-ietf-sip-outbound-08 (work in progress), March 2007.
[RFC0959] Postel, J. and J. Reynolds, "File Transfer Protocol",
STD 9, RFC 959, October 1985.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
[RFC4510] Zeilenga, K., "Lightweight Directory Access Protocol
(LDAP): Technical Specification Road Map", RFC 4510,
June 2006.
[RFC4825] Rosenberg, J., "The Extensible Markup Language (XML)
Configuration Access Protocol (XCAP)", RFC 4825, May 2007.
Authors' Addresses
Daniel Petrie
SIPez LLC.
34 Robbins Rd
Arlington, MA 02476
USA
Email: dan.ietf AT SIPez DOT com
URI: http://www.SIPez.com/
Sumanth Channabasappa (Editor)
CableLabs
858 Coal Creek Circle
Louisville, Co 80027
USA
Email: sumanth@cablelabs.com
URI: http://www.cablelabs.com/
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Full Copyright Statement
Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
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Petrie & Channabasappa, Ed. Expires November 2, 2007 [Page 64]
